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pg_walinspect: pg_get_wal_fpi_info() -> pg_get_wal_block_info()

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This commit reworks pg_get_wal_fpi_info() to become aware of all the
block information that can be attached to a record rather than just its
full-page writes:
- Addition of the block id as assigned by XLogRegisterBuffer(),
XLogRegisterBlock() or XLogRegisterBufData().
- Addition of the block data, as bytea, or NULL if none.  The length of
the block data can be guessed with length(), so there is no need to
store its length in a separate field.
- Addition of the full-page image length, as counted without a hole or
even compressed.
- Modification of the handling of the full-page image data.  This is
still a bytea, but it could become NULL if none is assigned to a block.
- Addition of the full-page image flags, tracking if a page is stored
with a hole, if it needs to be applied and the type of compression
applied to it, as of all the BKPIMAGE_* values in xlogrecord.h.

The information of each block is returned as one single record, with the
record's ReadRecPtr included to be able to join the block information
with the existing pg_get_wal_records_info().  Note that it is perfectly
possible for a block to hold both data and full-page image.

Thanks also to Kyotaro Horiguchi and Matthias van de Meent for the
discussion.

This commit uses some of the work proposed by Melanie, though it has
been largely redesigned and rewritten by me.  Bharath has helped in
refining a bit the whole.

Reported-by: Melanie Plageman
Author: Michael Paquier, Melanie Plageman, Bharath Rupireddy
Discussion: https://postgr.es/m/CAAKRu_bORebdZmcV8V4cZBzU8M_C6tDDdbiPhCZ6i-iuSXW9TA@mail.gmail.com
This commit is contained in:
Michael Paquier
2023-03-10 10:09:07 +09:00
parent 8da2ec31ee
commit 9ecb134a93
5 changed files with 174 additions and 86 deletions
Download Patch File Download Diff File Expand all files Collapse all files

140
contrib/pg_walinspect/pg_walinspect.c
View File

@@ -20,6 +20,7 @@
#include "access/xlogutils.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/pg_lsn.h"
@@ -30,7 +31,7 @@
PG_MODULE_MAGIC;
PG_FUNCTION_INFO_V1(pg_get_wal_fpi_info);
PG_FUNCTION_INFO_V1(pg_get_wal_block_info);
PG_FUNCTION_INFO_V1(pg_get_wal_record_info);
PG_FUNCTION_INFO_V1(pg_get_wal_records_info);
PG_FUNCTION_INFO_V1(pg_get_wal_records_info_till_end_of_wal);
@@ -56,7 +57,7 @@ static void FillXLogStatsRow(const char *name, uint64 n, uint64 total_count,
Datum *values, bool *nulls, uint32 ncols);
static void GetWalStats(FunctionCallInfo fcinfo, XLogRecPtr start_lsn,
XLogRecPtr end_lsn, bool stats_per_record);
static void GetWALFPIInfo(FunctionCallInfo fcinfo, XLogReaderState *record);
static void GetWALBlockInfo(FunctionCallInfo fcinfo, XLogReaderState *record);
/*
* Check if the given LSN is in future. Also, return the LSN up to which the
@@ -221,49 +222,40 @@ GetWALRecordInfo(XLogReaderState *record, Datum *values,
/*
* Store a set of full page images from a single record.
* Store a set of block information from a single record (FPI and block
* information).
*/
static void
GetWALFPIInfo(FunctionCallInfo fcinfo, XLogReaderState *record)
GetWALBlockInfo(FunctionCallInfo fcinfo, XLogReaderState *record)
{
#define PG_GET_WAL_FPI_INFO_COLS 7
#define PG_GET_WAL_BLOCK_INFO_COLS 11
int block_id;
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
for (block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++)
{
PGAlignedBlock buf;
Page page;
bytea *raw_page;
BlockNumber blk;
DecodedBkpBlock *blk;
BlockNumber blkno;
RelFileLocator rnode;
ForkNumber fork;
Datum values[PG_GET_WAL_FPI_INFO_COLS] = {0};
bool nulls[PG_GET_WAL_FPI_INFO_COLS] = {0};
Datum values[PG_GET_WAL_BLOCK_INFO_COLS] = {0};
bool nulls[PG_GET_WAL_BLOCK_INFO_COLS] = {0};
int i = 0;
if (!XLogRecHasBlockRef(record, block_id))
continue;
if (!XLogRecHasBlockImage(record, block_id))
continue;
blk = XLogRecGetBlock(record, block_id);
page = (Page) buf.data;
if (!RestoreBlockImage(record, block_id, page))
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg_internal("%s", record->errormsg_buf)));
/* Full page exists, so let's save it. */
(void) XLogRecGetBlockTagExtended(record, block_id,
&rnode, &fork, &blk, NULL);
&rnode, &fork, &blkno, NULL);
values[i++] = LSNGetDatum(record->ReadRecPtr);
values[i++] = ObjectIdGetDatum(rnode.spcOid);
values[i++] = ObjectIdGetDatum(rnode.dbOid);
values[i++] = ObjectIdGetDatum(rnode.relNumber);
values[i++] = Int64GetDatum((int64) blk);
values[i++] = Int16GetDatum(block_id);
values[i++] = ObjectIdGetDatum(blk->rlocator.spcOid);
values[i++] = ObjectIdGetDatum(blk->rlocator.dbOid);
values[i++] = ObjectIdGetDatum(blk->rlocator.relNumber);
values[i++] = Int64GetDatum((int64) blkno);
if (fork >= 0 && fork <= MAX_FORKNUM)
values[i++] = CStringGetTextDatum(forkNames[fork]);
@@ -272,34 +264,102 @@ GetWALFPIInfo(FunctionCallInfo fcinfo, XLogReaderState *record)
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg_internal("invalid fork number: %u", fork)));
/* Initialize bytea buffer to copy the FPI to. */
raw_page = (bytea *) palloc(BLCKSZ + VARHDRSZ);
SET_VARSIZE(raw_page, BLCKSZ + VARHDRSZ);
/* Block data */
if (blk->has_data)
{
bytea *raw_data;
/* Take a verbatim copy of the FPI. */
memcpy(VARDATA(raw_page), page, BLCKSZ);
/* Initialize bytea buffer to copy the data to */
raw_data = (bytea *) palloc(blk->data_len + VARHDRSZ);
SET_VARSIZE(raw_data, blk->data_len + VARHDRSZ);
values[i++] = PointerGetDatum(raw_page);
/* Copy the data */
memcpy(VARDATA(raw_data), blk->data, blk->data_len);
values[i++] = PointerGetDatum(raw_data);
}
else
{
/* No data, so set this field to NULL */
nulls[i++] = true;
}
Assert(i == PG_GET_WAL_FPI_INFO_COLS);
if (blk->has_image)
{
PGAlignedBlock buf;
Page page;
bytea *raw_page;
int bitcnt;
int cnt = 0;
Datum *flags;
ArrayType *a;
page = (Page) buf.data;
/* Full page image exists, so let's save it */
if (!RestoreBlockImage(record, block_id, page))
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg_internal("%s", record->errormsg_buf)));
/* Initialize bytea buffer to copy the FPI to */
raw_page = (bytea *) palloc(BLCKSZ + VARHDRSZ);
SET_VARSIZE(raw_page, BLCKSZ + VARHDRSZ);
/* Take a verbatim copy of the FPI */
memcpy(VARDATA(raw_page), page, BLCKSZ);
values[i++] = PointerGetDatum(raw_page);
values[i++] = UInt32GetDatum(blk->bimg_len);
/* FPI flags */
bitcnt = pg_popcount((const char *) &blk->bimg_info,
sizeof(uint8));
/* Build set of raw flags */
flags = (Datum *) palloc0(sizeof(Datum) * bitcnt);
if ((blk->bimg_info & BKPIMAGE_HAS_HOLE) != 0)
flags[cnt++] = CStringGetTextDatum("HAS_HOLE");
if (blk->apply_image)
flags[cnt++] = CStringGetTextDatum("APPLY");
if ((blk->bimg_info & BKPIMAGE_COMPRESS_PGLZ) != 0)
flags[cnt++] = CStringGetTextDatum("COMPRESS_PGLZ");
if ((blk->bimg_info & BKPIMAGE_COMPRESS_LZ4) != 0)
flags[cnt++] = CStringGetTextDatum("COMPRESS_LZ4");
if ((blk->bimg_info & BKPIMAGE_COMPRESS_ZSTD) != 0)
flags[cnt++] = CStringGetTextDatum("COMPRESS_ZSTD");
Assert(cnt <= bitcnt);
a = construct_array_builtin(flags, cnt, TEXTOID);
values[i++] = PointerGetDatum(a);
}
else
{
/* No full page image, so store NULLs for all its fields */
memset(&nulls[i], true, 3 * sizeof(bool));
i += 3;
}
Assert(i == PG_GET_WAL_BLOCK_INFO_COLS);
tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
values, nulls);
}
#undef PG_GET_WAL_FPI_INFO_COLS
#undef PG_GET_WAL_FPI_BLOCK_COLS
}
/*
* Get full page images with their relation information for all the WAL
* records between start and end LSNs. Decompression is applied to the
* blocks, if necessary.
* Get information about all the blocks saved in WAL records between start
* and end LSNs. This produces information about the full page images with
* their relation information, and the data saved in each block associated
* to a record. Decompression is applied to the full page images, if
* necessary.
*
* This function emits an error if a future start or end WAL LSN i.e. WAL LSN
* the database system doesn't know about is specified.
*/
Datum
pg_get_wal_fpi_info(PG_FUNCTION_ARGS)
pg_get_wal_block_info(PG_FUNCTION_ARGS)
{
XLogRecPtr start_lsn;
XLogRecPtr end_lsn;
@@ -317,7 +377,7 @@ pg_get_wal_fpi_info(PG_FUNCTION_ARGS)
xlogreader = InitXLogReaderState(start_lsn);
tmp_cxt = AllocSetContextCreate(CurrentMemoryContext,
"pg_get_wal_fpi_info temporary cxt",
"pg_get_block_fpi_info temporary cxt",
ALLOCSET_DEFAULT_SIZES);
while (ReadNextXLogRecord(xlogreader) &&
@@ -326,7 +386,7 @@ pg_get_wal_fpi_info(PG_FUNCTION_ARGS)
/* Use the tmp context so we can clean up after each tuple is done */
old_cxt = MemoryContextSwitchTo(tmp_cxt);
GetWALFPIInfo(fcinfo, xlogreader);
GetWALBlockInfo(fcinfo, xlogreader);
/* clean up and switch back */
MemoryContextSwitchTo(old_cxt);